Wastewater trickle tower(s) controlling and grooming cross-reference to related application

ABSTRACT

A wastewater treatment apparatus has a manifold interconnecting two or more trickle towers to enable wastewater to be sequentially moved through the trickle towers in different selective sequences. One or more sensors may sense the growth of biogrowth in the trickle towers, and when the sensed growth reaches a predetermined value, valves or other parts change the interconnection of the manifold to the trickle towers to change the sequence in which the wastewater moves through the trickle towers. A method of treating wastewater includes changing the sequence of flow through the trickle towers to achieve manual or automatic grooming of the biogrowth on the biomedia, so both improving the overall efficiency of the system and also prolonging its running time between maintenance shutdowns. Another embodiment has one or more trickle towers with suspended strands of biomedia down which the wastewater passes; a sensor senses increase in growth of biomass on at least a portion of the biomedia.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority of U.S. ProvisionalApplication Serial No. 60/368,344 filed Mar. 28, 2002.

FIELD OF THE INVENTION

[0002] This invention relates to the treatment of wastewater using oneor more trickle towers employing biomedia. The invention particularlyrelates to the accumulation of biogrowth on the biomedia.

BACKGROUND OF THE INVENTION

[0003] With greater demands being placed on the treatment of wastewaterby regulatory authorities, there has become a growing need for systemsthat will treat wastewater to a higher level of purity. This has alsobrought an increasing need for systems that are more versatile in designand can more readily be adapted to handle differing wastewater treatmentrequirements.

[0004] I have found that a trickle tower system employing strands oflooped cord biomedia is more suited to handling today's increasingdemands in wastewater treatment than the conventional systems currentlyin use. The initial approach of a looped cord biomedia trickle towersystem is disclosed in my U.S. Pat. No. 6,241,889 published Jun. 5,2001. While this trickle tower system has been promising, and thegeneral approach employed appears correct, further improvements andmodifications are now desirable for more widespread adoption by industryand civil authorities.

SUMMARY OF THE INVENTION

[0005] This invention is concerned with modifying and improving thewastewater treatment process and apparatus disclosed in the above U.S.Pat. No. 6,241,889 the whole disclosure of which is hereby incorporatedherein by reference.

[0006] This invention is also concerned with developing furtherapproaches to trickle tower treating of wastewater. Some of theseapproaches are particularly advantageous with looped cord biomedia, andothers are advantageous with other biomedia and other systems inaddition to being applicable with looped cord biomedia.

[0007] This invention is particularly concerned with controlling thegrowth of biogrowth on the biomedia in a trickle tower. In this way, bykeeping this biogrowth to a manageable level, the trickle towercontinuous to function to an acceptable level of efficiency in treatingthe wastewater. With a single trickle tower operation, the presentinvention can be employed to indicate when the biomedia needs cleaningor replacing. With a multi-trickle tower operation, the presentinvention can provide for manual or automatic grooming of the biomedia,so both improving the overall efficiency of the system and alsoprolonging its running time between maintenance shutdowns.

[0008] According to one aspect of the present invention, there isprovided a wastewater treatment apparatus comprising a plurality oftrickle towers containing biomedia, a plurality of wastewater dischargemeans for discharging wastewater at upper ends of the trickle towers toenable the wastewater to pass down the biomedia, and receptaclesadjacent lower ends of the trickle towers for catching wastewaterfalling from the biomedia. Moving means are associated with the trickletowers for moving wastewater from the receptacles to the discharge meansto enable wastewater to recirculate through the trickle towers. Manifoldmeans is provided, interconnecting the trickle towers, and includingselectively operable parts, for enabling wastewater to be sequentiallymoved through the trickle towers in different selective sequences.

[0009] The moving means preferably comprises one or more pumpsassociated with each trickle tower, but may comprise a water lift orconveyor.

[0010] The selectively operable parts preferably comprise valves forchanging the path of flow of the wastewater, but alternatively oradditionally may comprise disconnectable, reconnectable, and movableconduits, hoses, etc.

[0011] The biomedia may comprise strands of looped cord that preferablyextend vertically and may be held under tension by tensioning means.

[0012] The tensioning means preferably comprises tensioning bolts bywhich the biomedia is supported or tensioning bolts at the bottom of thebiomedia, but may comprise resilient members above or below the biomediaor weights at the bottom of the biomedia.

[0013] The manifold means preferably comprises a pipe system, but mayalternatively or additionally comprise troughs, ducts, passageways, etc.A control system may be connected to the selectively operable parts andprogrammable to selectively operate these parts.

[0014] The wastewater discharge means may comprise rotating spraynozzles, alternatively or in addition the wastewater discharge means maycomprise stationary spray nozzles. The wastewater discharge means maycomprise an oscillating slot nozzle for cascading a sheet of wastewaterback and forth over the biomedia.

[0015] The receptacles may comprise base trays with base recirculatingtanks spaced from and connected to these base trays. On the other hand,the receptacles may be base recirculating tanks themselves.

[0016] Sensing means is preferably provided for sensing the amount ofbiogrowth accumulating on the biomedia in at least one of the trickletowers during operation.

[0017] The sensing means may provide an output signal. An indicator maybe provided responsive to the signal, to provide an indication of theaccumulation of the biogrowth in the particular trickle tower. Thesignal may be arranged to cause actuation of at least one selectivelyoperable part when the amount of biogrowth accumulation reaches apredetermined level.

[0018] The sensing means may cause a plurality of the parts, e.g.valves, to be actuated to change the sequence of flow of the wastewaterthrough the trickle towers upon the amount of biogrowth accumulationreaching a predetermined level.

[0019] The sensing means may comprise a yieldable member yieldable toincrease in weight of at least a part of the biomedia. The yieldablemember may comprise a spring. On the other hand, the yieldable membermay comprise a load cell, a piezoelectric device, a potentiometer, aninduction coil device, a fluidic system, a hydraulic system, etc. Thesensing means may comprise instead, or in addition, a light or otherelectromagnetic beam sensing system or a system for sensing changes inmass. Conveniently, the sensing means may comprise a device sensitive tochanges in tension or length of one or more strands of biomedia, whenthe biomedia is in strand form.

[0020] The apparatus may include a support structure, and the yieldablemember may be connected between the support structure and at least aportion of the biomedia.

[0021] In a preferred embodiment, the apparatus includes weightsensitive means, responsive to increase in weight of at least a part(e.g. one or more strands) of the biomedia due to accumulation ofbiogrowth thereon, for causing operation of valves to change thesequence of movement of the wastewater through the trickle towers.

[0022] In another preferred embodiment, the apparatus includes sensingmeans associated with each trickle tower for independently sensingbiogrowth on the biomedia in that tower, and for causing operation ofvalves to change the sequence in which the wastewater moves through thetrickle towers so that the tower with the largest biogrowth is placedlast in the sequence. In this way, the system can become at leastpartially self-grooming. This sensing means may sense weight or mass orboth.

[0023] According to another aspect of the invention, there is provided awastewater treatment apparatus comprising a plurality of trickle towers,each tower containing one or more cells, and each cell containing aplurality of vertically extending strands of biomedia. The towers areinterconnected for the wastewater to pass through them in sequence,valves being associated with the towers for changing the sequence. Meansis included, responsive to changes in weight and connected to at least aportion of the biomedia in at least one of the cells, for sensingincrease in weight due to biogrowth forming on that biomedia, and forcausing operation of at least one of the valves to change the sequencewhen a predetermined weight increase is sensed.

[0024] The means for sensing increase in weight may comprise a springconnected between the at least a portion of the biomedia and the trickletower of that portion, the spring at least partly supporting thatportion.

[0025] The strands may comprise looped cord biomedia, and are preferablytensioned vertically in the towers.

[0026] According to yet another aspect of the invention, there isprovided a wastewater treatment apparatus comprising a trickle towerhaving a supporting structure, strands of biomedia suspended from thissupport structure with wastewater, when being treated, passingdownwardly over the biomedia, and means for sensing increase in weightof the biomedia due to biogrowth forming thereon.

[0027] According to yet another aspect of the invention, there isprovided a method of treating wastewater comprising the steps ofintroducing a supply of wastewater into a first trickle tower containingbiomedia and circulating this wastewater therethrough, the wastewatertrickling down the biomedia and becoming partially treated. After atime, passing the wastewater to a second trickle tower containingbiomedia and circulating the wastewater therethrough to further treatthe partially treated wastewater. Allowing biogrowth to build on thebiomedia in said trickle towers, sensing increase in weight of thebiomedia in each of the trickle towers due to the increase in biogrowth,and upon the sensed increase in weight of the biomedia in the firsttrickle tower reaching a predetermined value, switching the sequence offlow of the wastewater through the trickle towers by introducing thesupply of wastewater into the second trickle tower for the first partialtreatment and then subsequently circulating partially treated wastewaterthrough the first trickle tower.

[0028] Subsequent to the increase in weight of the biomedia in thesecond trickle tower reaching a predetermined value, the sequence offlow of the wastewater through the trickle towers may be switched tointroduce the supply of wastewater into the first trickle tower for thefirst partial treatment thereof.

[0029] There may be more than two trickle towers in the sequence of flowof the wastewater through the trickle towers, and the sequence of flowis preferably switched each time the sensed increase in weight of thebiomedia in one of the trickle towers reaches a predetermined value.

[0030] According to yet another aspect of the invention, there isprovided a method of treating wastewater comprising the steps of passingwastewater sequentially through a series of trickle towers, thewastewater to be treated being introduced at one tower and the fullytreated wastewater exiting the series at another tower, monitoring thegrowth of biogrowth in each of the towers, and when the growth ofbiogrowth in any particular tower reaches a threshold value, switchingthe sequence in which the wastewater passes through the series oftrickle towers to cause the fully treated wastewater to exit the seriesat this particular tower.

[0031] The towers may contain strands of biomedia, and the monitoringcomprise suspending at least one of the biomedia strands in each towervia a weight sensitive device sensitive to any increase in weight of thesuspended biomedia, the increase in weight indicating the amount ofbiomass growth. The weight sensitive device may comprise a spring (orany of the devices previously mentioned), the increase in weight of thebiomedia portion acting upon the spring or other device and, upon thethreshold value being reached, causing actuation of a control systemwhich effects the switching of the sequence.

[0032] Other objects, features, and advantages of the present inventionwill become more fully apparent from the following detailed descriptionof the preferred embodiments, the appended claims, and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In the accompanying drawings, in which like reference charactersin the same or different Figures indicate like parts:

[0034]FIG. 1 is a schematic vertical section, looking in a front viewdirection, of a trickle tower wastewater treatment apparatus embodyingthe present invention;

[0035]FIG. 2 is a schematic elevational side view, partly in section, ofanother version of the apparatus of FIG. 1;

[0036]FIG. 3 is schematic front view of the apparatus of FIG. 2 in asimilar direction to the view in FIG. 1;

[0037]FIG. 4 is a diagrammatic elevational view, partly in section, of awastewater spraying system employed in the apparatuses of FIGS. 1 and 2;

[0038]FIG. 5 is a diagrammatic perspective view of a biomedia hangerframe;

[0039]FIG. 6 is a diagrammatic simplified perspective view of a biomediagrate made up of a plurality of the hanger frames of FIG. 5, andemployed in the apparatuses of FIGS. 1, 2, and 3;

[0040]FIG. 7 is a plan view of the grate of FIG. 6;

[0041]FIG. 8 is an end view (partially in section) of the upperstructure of the grate in the direction of the arrow 8 in FIG. 7;

[0042]FIG. 9 is an exploded view of FIG. 8 additionally showing aportion of a strand of biomedia;

[0043]FIG. 10 is a simplified elevational view, partly in section, of acell of a trickle tower illustrating a first biogrowth sensingembodiment according to the invention;

[0044]FIG. 11 illustrates a modification of the base receptacle of thetrickle tower of FIG. 10 with a side wall of the base receptacleomitted;

[0045]FIG. 12 is a diagrammatic elevational representation of the basetanks and an interconnecting manifold for grooming biogrowth accordingto another embodiment of the invention in a three trickle tower system;

[0046]FIG. 13 is a diagrammatic expanded plan view of the base tanks andmanifold of FIG. 12;

[0047]FIG. 14 is an elevational view, partly in section, of an upperportion of a trickle tower showing a second biogrowth sensing embodimentaccording to the invention;

[0048]FIG. 15 is a diagrammatic plan view of the embodiment of FIG. 14;

[0049]FIG. 16 is a simplified view in the direction of the arrow 16 inFIG. 14;

[0050]FIG. 17 is an enlarged view of the circled portion 17 of FIG. 16;

[0051]FIG. 18 is an enlarged exploded view from the rectangular portion18 in FIG. 16;

[0052]FIG. 19 is an electrical schematic of a warning system of thebiomass sensing arrangement of the embodiment of FIG. 10; and

[0053]FIG. 20 is an electrical schematic of a biogrowth grooming systemof a combined embodiment of FIGS. 12 through 18.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054]FIG. 1 shows an exterior, weatherproof, steel building 2 having asupport structure 4 erected on a concrete base 6, with a coveredrecirculation tank 8 outside the building. Two wastewater treatmentcells 10 are shown. Each cell 10 has an upper closure hood 12, with aflexible curtain 14 draped around the hood 12 and extending downwardlyinto a base receptacle 16 formed on the concrete base 6. Biomedia 18 isenclosed by the curtain 14, and a wastewater discharge system 20 ismounted inside the hood 12 above the biomedia, both as shown throughbroken away portions of the left cell 10. Wastewater 22 from thedischarge system 20 flows down the biomedia 18 and drips into the basereceptacle 16, illustrated as a base tray, from which the partiallytreated wastewater flows to the recirculation tank 8 for recirculationto the system 20 of the same or another cell. Each cell 10 has its ownrecirculation tank. Of course, each base tray 16 could be constructed asa recirculation tank, so eliminating outside recirculation tanks 8. Thehoods 12 are suspended by structural members 24, 26 supported by andforming part of the building structure 4, for example the roof rafters.The curtains 14 are attached and sealed to the outside of the hoods 12,and to the inside of the base receptacles 16. One or more releasablefasteners may extend vertically up and down each curtain for releasablyopening and closing the curtain during assembly of the curtain, and foraccessing the biomedia within the curtain. The biomedia 18 preferablycomprises vertical strands of looped cord biomedia, but may comprisestrands in the form of strips of plastic, or may be solid biomedia.

[0055]FIG. 2 illustrates in side view a variant of the apparatus of FIG.1 and shows an elongate treatment cell 10 surrounded by a curtain 14. Atthe top of this cell 10 are five wastewater spray units 20 fed by acommon supply pipe 28. An elongate base receptacle 16, with a downwardlyinclined floor 30, communicates with an external free-standingrecirculation tank 32 via pipes 34 and pumps 36, 38, which effectrecirculation of the wastewater through the cell 10. The pump 36 drawspartially treated wastewater from the base tray 16 via a suction pipe40. A valve 42 directs the wastewater to the common supply pipe 28 forrecirculation through the cell 10. Excess wastewater is directed by thevalve 42 to the recirculation tank 32 via pipe 44. Excess wastewaterspilling out of the tank 32 is directed by a continuation (not shown) ofthe outlet pipe 46 back to the base tray 16. The pump 38 can be used forinitial priming of the system and, if necessary, to supplement the pump36. Initial entry of untreated wastewater, or partially treatedwastewater from another trickle tower of the apparatus, enters the tank32 via inlet pipe 48.

[0056]FIG. 3 is a front view of the apparatus of FIG. 2, and shows foursimilar treatment cells 10 side by side. Each of these cells 10, and thebiomedia therein, is surrounded and contained by a separate curtain 14.By viewing FIG. 3 in conjunction with FIG. 2, it will be realized thateach cell 10 has an elongated rectangular horizontal cross-section. FIG.3 is a similar view to the two cells 10 in FIG. 1, and the four cells 10in FIG. 3 are housed in a building similar to that shown in FIG. 1.

[0057] When the horizontal cross-section of a cell is circular, arotating spray device, such as shown and described in previouslyreferenced U.S. Pat. No. 6,241,889, would be satisfactory. However, withnon-circular horizontal cross-sections, for instance square, oval, andrectangular cross-sections, a circular spray pattern may leave cornerand/or end or other sections starved of sprayed wastewater. To overcomethis, stationary spray nozzles may additionally be placed in thecorners, or any other area missed by the circular spray pattern. Thesestationary nozzles preferably should be given a pulsing action toprovide the sprayed biomedia with an opportunity to receive alternatelywastewater and air. This pulsing can be achieved using power-operatedon/off valves, intermittent pumping, injectors, or an intermittent flowdiversion system. A preferred way of achieving this pulsing isillustrated in FIG. 4. Alternatively, an oscillating spray or dischargesystem could be employed, preferably oscillating about a horizontal axisextending across the cross-section of the biomedia. This can be achievedwith a cascade system comprising a horizontal oscillating manifoldhaving a longitudinal slot nozzle that cascades a sheet of wastewaterintermittently as the manifold oscillates. Although less preferable,instead of using rotating or oscillating sprays, all stationaryintermittent sprays could be employed.

[0058]FIG. 4 is a front view, partly in section, of the wastewaterspraying units 20 shown in FIGS. 1, 2, and 3. A branch of the wastewaterfeed pipe 28 is connected to an inlet port 50 in a body of the sprayunit 20, and communicating with an inlet in a rotating vertical pipe 54.This inlet is formed by a series of vertical slots 56 all around thewall of the rotating pipe 54, so providing continuous communicationbetween the pipes 28 and 54. The rotating pipe communicates at its lowerend, via a T-junction 58, with the center of the rotating spray arm 60.This rotating arm is schematically shown as having three nozzle orifices62 on each side of the vertical rotational axis, providing six jets ofspray 64; the total number of nozzle orifices could be two, four, six,eight, or more, depending on the size of the trickle tower cell and thecharacter of the wastewater being treated. Between the feed pipe 28 andthe spray bar 60, the rotating pipe 54 has a circular outlet orificethat sequentially communicates with four pulse nozzle outlets 66 (onlythree of which can be seen). These outlets 66 supply four stationarynozzles 68 (only two of which can be seen) with intermittent pulses ofwastewater. The jets of spray 70, which are sequentially ejecteddownwardly from the stationary nozzles 68, impinge upon an area of thebiomedia below that is either not covered, or not fully covered, by thesprays 64 issuing from the rotating spray arm 60. At the upper end ofthe shaft is mounted a pulley 72 connected, by a belt or chain 74, to adrive motor 76 mounted on the hood or a beam of the support structure.Schematically shown at 78 is another drive from the motor 76 forsimultaneously driving a second, or more, similar wastewater dischargeunits. The five systems 20 shown in FIG. 2 (being in a single cell)would be connected together by belts, or chains, or similartransmission, and driven by the single motor 76.

[0059] Also, in all of the above pulsing arrangements, instead of thepulse jets 70 issuing in a progressive sequence, they may issue in anysuitable sequence or, if particular circumstances required it, theycould all issue at the same time.

[0060]FIG. 5 illustrates a frame or hanger 90 of looped cord biomedia.The hanger frame 90 has a plurality of discrete lengths 92 of loopedcord biomedia extending between upper and lower pairs 94, 96 of hangerbars. The ends of the looped cord 92 are clamped between the respectivepairs of bars. The pairs of bars are secured together by gluing,although this could be done by spot welding, the bars preferably beingmade of plastic material, for example ABS. Each end of each pair of barshas a pair of vertically spaced-apart holes 98 for assembling aplurality of hangers together. When the pairs 94, 96 of bars arestretched apart, the lengths 92 of looped cord are spaced apart parallelto each other. The ends of the lengths of looped cord may be cut offflush with the adjacent pair of clamping bars, or may extend just beyondthe bars. In the latter case, these extending ends may be heat-treatedto cause them to fuse and form enlarged ends, to retain more securelythe ends from pulling through between the pair of clamping bars.

[0061] These hangers are preferably manufactured as a series of linksconnected together and rolled up into a somewhat cylindrical roll. Thisis done by forming a warp of strands of looped cord biomedia andclamping a pair of hanger bars across this warp. The warp is thenadvanced the desired length for the hanger, and another pair of hangerbars clamped across the warp. Thereafter, the warp is advanced a shortdistance (e.g. 1 to 4 inches) and another pair of hanger bars (to formthe beginning of the next hanger) clamped across the warp. This processcontinues with the hangers being reeled onto a spool as further hangersare formed. Individual hangers can be then cut from the spool asrequired. If the cutting is performed by a hot-air knife, the cut endsof the looped cord biomedia fuse as mentioned above.

[0062] The looped cord biomedia is preferably made from knittedpolyester or PVDC yarns. If the knitted structure enables the loops tobe orientated in one axial direction, then in the grate, all such loopsshould be orientated in the same direction. This is enabled by havingdiscrete cut lengths of biomedia formed from a warp. When assembled inthe trickle tower, all such loops would be orientated upwards.

[0063]FIG. 6 shows a plurality of hanger frames 90 connected together toform a grate 99. The upper pairs of hanger clamping bars 94 are rigidlybolted together by a pair of bolts 100 at each end through the holespreviously mentioned. The lower pairs of hanger clamping bars 96 aresimilarly rigidly bolted together by bolts 102. Spacers keep the pairsof bars correctly spaced apart.

[0064]FIG. 7 shows in plan view the top of the grate 99, although thepairs 94 of hanger bars are relatively longer than in FIG. 6. Elevenpairs of hanger bars are equally space apart by spacers 104 cut fromsquare aluminum tubing. With this longer grate 99, five pairs 100 ofequally spaced-apart bolts pass through the bars and the spacers. Inthis way, the upper pairs 94 of bars are rigidly secured together; thelower pairs of bars of this grate 99 are similarly rigidly securedtogether.

[0065]FIG. 8 is an end view (mostly in vertical section) of the upperhanger bars of the grate in the direction of the arrow 8 in FIG. 7 (thelower hanger bars would look the same). The connecting and securingbolts 100 are tightened by their nuts 106 at the right end in FIG. 8.The hollow spacer tubes 104 extend vertically between the pairs ofclamping bars for the full height thereof. FIG. 9 is an exploded view ofFIG. 8, but also showing a strand 18 of looped cord biomedia clampedbetween the right outermost pair of clamping bars and extendingdownwardly therefrom; the upper cut end 108 of the strand 18 can be seenextending slightly above the hanger bars. Although the strands ofbiomedia are clamped between the pairs of clamping bars before these areassembled into a grate, the subsequent tightening of the grate bolts 100further aids the securing of the biomedia ends. This improves theintegrity of the grate 99, and enables the biomedia strands to be ableto carry heavier weights of biomass, during operation when purifyingwastewater, because the biomass loaded strands further resist anytendency to pull through the upper clamping bars.

[0066]FIG. 10 shows a trickle tower 10 (with some parts omitted forclarity) having at the top a hood 12 suspended from a beam 24 of asupport structure (such as in FIG. 1), a base receptacle 16 at thebottom, and a flexible curtain 14 extending from around the hood down toinside the base receptacle. Four grates 99 of looped cord biomedia aresuspended from the hood 12 by tensioning bolts 110, the bottoms of thesegrates being anchored by further tensioning bolts 112 to one or morebars 114 extending across the base receptacle 16. The vertical,spaced-apart, parallel strands 92 of looped cord biomedia 18 aretensioned by adjusting the tensioning bolts 110, 112 at the top and/orbottom. The bottom bolts 112 are a sliding fit, i.e. a slip fit, throughthe anchoring bar(s) 114, this allowing the biogrowth-loaded strands 92to lengthen downwards as the biogrowth gets heavier. An individualstrand 116 of looped cord biomedia extends down through the trickletower cell 10 between the strands 92 of one of the grates 99; thisstrand 116 is suspended at the top from a cable 118, and is weighted atthe bottom by a free hanging weight 120. The weight preferably placesthis individual strand 116 under approximately the same tension as thetensioned strands 92 of the four grates. This weight 120 may be guidedin a guide tube to help more accurately locate the individual strand andminimize the risk of it touching adjacent strands. The cable 118 passesthrough a thin 122 extending across the top of the cell above the grates99, and then down the outside of the curtain 14 to adjacent the bottomthereof The free end 124 of the cable 118 is anchored in, or to orthrough, a sensing device 126 (shown schematically) for sensing changein weight due to increase in biogrowth. This is done by sensing movementand converting such movement into a signal, or by actuating anelectrical device, such as a switch. When the weighted individual strand116 has moved the end 124 of the cable 118 a predetermined distance,indicative of the amount of biogrowth on the strand 116, a visual,audible, electrical, and/or mechanical signal is produced. With a singletrickle tower installation, this signal provides a warning that thebiomedia is loaded with biogrowth, and requires cleaning or changing.With a multi-tower installation, this signal can give a similar warning,and/or can effect valve changes to alter the path of flow of thewastewater through the trickle towers, as will be described later. Thewarning signal can be a light, e.g. a flashing lamp, a buzzer, a klaxon,or a mechanical signal device, and/or may make an entry in a computermonitoring system. The sensing device can be an induction coil, apotentiometer, a variable resistance, a variable condenser, or a switch,etc. having a movable component and a stationary part. The relationshipbetween the movement of the individual strand 116 and cable 118, or theincrease in tension thereof, and the amount of biogrowth on the strand116, is determined experimentally, and the sensing device 126 calibratedaccordingly. Although, preferably, the movement of the end 124 of thecable 118 outside the particular trickle tower cell is utilized, thedownward movement of the weight 120 inside the trickle tower or theincrease in tension of the strand 116 or cable 118 could be utilized toproduce the warning signal or effect any valve changes.

[0067]FIG. 11 illustrates a modification to the anchoring of the bottomof the grates 99. Instead of anchoring the grates inside the base tank16, the tensioning bolts 112 pass through the bottom 128 of the tank,and are tensioned by nuts 130 outside the tank 16. To enable thetensioning bolts 112 to freely pass through the tank bottom 128 as thebiogrowth-loaded strands 92 lengthen, tubes 132 sealably extend throughthe tank bottom and extend upwardly to above the wastewater level 134 inthe tank. The tensioning bolts 112 are a slip fit in these tubes 132.The weighted strand 116 in FIG. 10 could have an extension thatsimilarly passes through a tube in the bottom of the tank, the weightthen being outside the tank.

[0068]FIG. 12 represents a multi-tower system having three wastewatertrickle towers interconnected at their recirculation base tanks 136 by amanifold 138. The three towers are labeled A, B, and C, only the basetanks 136 of these towers being shown. The manifold comprises four pipes141, 142, 143, 144 interconnectable in various sequences between therecirculation tanks 136 of the three towers. The four pipes 141 to 144are schematically shown parallel and one above the other. Wastewaterenters the system through the left end 146 of the upper pipe 141, andthe fully treated wastewater exits the system through the right end 148of the lowest pipe 144. All four pipes are connected by valves 151, 153,155, 157 to the trickle tower A, and all four pipes are connected byvalves 152, 154, 156, 158 to the tower C. Additionally, the middle twopipes 142, 43 are connected by open connections 159, 160 to the middletower B. The wastewater always enters the system at the left end inlet146 of the upper pipe 141, and exits the system at the right end outlet148 of the bottom pipe 144; in-between, the wastewater passes throughthe towers A, B, C in different sequences depending upon the settings ofthe valves, as will more readily be understood with reference to FIG.13.

[0069]FIG. 13 schematically shows, in expanded plan view, theconnections of each pipe 141, 142, 143, 144 of the manifold 138 to therecirculation tanks 136 of the trickle towers A, B, and C. The block 162represents an outer support structure, e.g. a weatherproof building,surrounding the three trickle towers. As explained with FIG. 12, thewastewater enters the system at 146 and exits the system at 148. Inbetween, the wastewater is recirculated many times through each of thetrickle towers A, B, and C; the partially treated wastewater after beingso treated in one of the trickle towers, then passing to a second of thetowers for recirculation therein, and then finally passing to the thirdof the towers for further recirculation therein before exiting at 148.The sequence of passage through the towers is first in the order A, B,C. Then as the amount of biogrowth on the biomedia in the first tower Agrows and reaches an amount that starts to seriously decrease theefficiency of processing the wastewater, the sequence is changed to theorder C, B, A. This sequence is continued until the biogrowth in tower Creaches an undesirable amount, and at that stage the sequence is changedback to A, B, C. This changing of the sequence continues to repeat eachtime the biogrowth, in which ever is the then leading tower (i.e. wherethe untreated wastewater initially enters the system), reaches anundesirable amount of biomass.

[0070] For the sequence A-B-C, the valves 151, 153, 156, 158 are open,as are connections 159,160; and valves 152, 154, 155, 157 are closed.For the sequence C-B-A, valves 152, 154, 155, 157 are open (as areconnections 159, 160), and valves 151, 153, 156, 158 are closed.

[0071] The biogrowth grows (or increases) at the fastest rate in thefirst tower entered by the wastewater. The second tower entered istreating already partially treated wastewater, and has a slower rate ofgrowth of biogrowth. The last tower entered is treating moderately purewastewater, and consequently has a relatively low rate of growth ofbiogrowth. By switching the initial intake of wastewater from the firsttower to the last tower, the first tower now receives moderately purewastewater which does not have sufficient “food” to feed themicroorganisms on its biomedia. Consequently, atrophy occurs and thebiomass starts decreasing in the first tower. At the same time, the rateof growth of biomass increases in the last tower as this is now handlinguntreated wastewater containing a full supply of “food”. The middletower remains the second in the treatment sequence, and continues tohave only a moderate amount of biomass growth. With this sequencing, thewastewater system can be run for an extended period of time, e.g.several months or possibly even a year (depending on the content of thewastewater), before needing attention to the state of the biomedia.

[0072] In stead of always leaving the tower B as the second in thesequence, valves could be placed between the four manifold pipes 141,142, 143, and 144 and the middle tower B, and then the sequencing wouldbe: A-B-C; B-C-A; C-A-B before returning to A-B-C etc. Such completerotation in the sequencing would extend further the time betweencleaning or replacing the biomedia. When there are four or more trickletowers, it is preferable to employ complete rotation in the sequencing,so that each tower takes its turn at being last in the sequence.

[0073] When changing the sequence through the towers of a multi-towersystem, the various valves (or movable pipe connections) can be changedmanually or automatically. When manual changing is employed, preferablythere is an arrangement for sensing biomass growth, e.g. as in FIG. 10,and a warning signal of some type triggered. On the other hand, themanual changeover could be based on a predetermined time cycle, or onphysical inspection of the state of the biomedia in the lead trickletower.

[0074] FIGS. 14 to 18 illustrate another approach to sensing the growthof biomass on the biomedia 18. In this approach, one or more biomediagrates in a trickle tower are sensed for change in weight. The trickletower is similar to those shown in FIGS. 1, 2, and 10, and preferablyemploys grates with looped cord biomedia, although any other type ofbiomedia, such as strips of plastic, strips of cloth, etc., could beused. Several of these trickle towers may be connected together by amanifold arrangement along the lines of that described with reference toFIGS. 12 and 13, and manual or automatic sequence changing employed.

[0075]FIG. 14 shows a biomedia grate 99 suspended by suspension bolts164 on each side and which pass upwardly with a slip fit through thehood 12 of the cell and structural members 24 supporting the hood. Thebolts 164 are supported on the structural members 24 by coil springs 166through which they freely pass. An upper washer and adjustable nut stopeach bolt from pulling downwards through its spring. The weight of thebiomedia grate 99 causes the springs 166 to compress to a certainextent. As the weight of biogrowth on the biomedia 18 increases, thesprings further compress so causing the bolts 164 to move progressivelydownwards.

[0076]FIG. 15 shows in plan view four grates 99 making up the cell. Themiddle two grates are suspended on each side by a pair of springs 166. Abar 172 is interconnected between each pair of springs, and a switchtrigger 174 is mounted at the center of this bar. Thus, the middle twogrates are spring mounted and between them carry four switch triggers174. This arrangement provides a balance between economy and weightchange sensitivity. However, any number of grates 99 could be sosupported from one to all four; and a switch trigger could be located atonly one side of a grate.

[0077]FIG. 16 shows an upper portion of one grate 99 in the direction ofthe arrow 16 in FIG. 14. The switch trigger can be more clearly seenintermediate the length of the bar 172. On the structural member 24,immediately below the switch trigger, is a switch body that is actuatedby the trigger. FIG. 17 shows the detail within the circle 17 in FIG.16, and more clearly shows the switch trigger 174 and its spacing abovean actuating plunger 178 protruding from the switch body 176. A lockingnut 180 locks any adjustment made with an adjusting knob 182 on ascrew-threaded stud 184 threadedly engaged in an elongate nut 186 fixedto the bar 172. FIG. 18 shows the detail within the box 18 in FIG. 16,and is an exploded view of the spring and bolt assembly.

[0078] As the biomass weight builds on the biomedia strands of thegrates, the increasing weight of the grates steadily compresses thesprings until one or more of the switch triggers descend sufficiently toactuate one or more of the switches. Actuation of at least one of theswitches 176 in the trickle tower causes a warning signal to be given,and/or effects automatic actuation of the valves in a manifold,interconnecting a plurality of trickle towers, to change the sequence offlow of the wastewater through the series of towers. The amount ofbiogrowth that occurs before one of the switches is triggered can becontrolled by adjusting the adjusting knobs 182 of the triggers 174. Theswitch is a simple on/off type, but this could be replaced by a variabletype of switch, such as a potentiometer, a rheostat, an induction coil,etc., for progressive weight measurement. Although it is preferred tohave the springs and triggers adjacent the top of each trickle tower, soreducing exposure to and contamination by wastewater, they could belocated adjacent the bottom of the towers and function in relationshipwith the lower bars of the grates. In another form, actuating membersmay slidably pass through the bottom of the base receptacle, such asthrough the tubes 132 in FIG. 11; these actuating members could beattached to the lower bars of the grates and be moved downwards by alengthening of the biomedia strands due to increase in biomass thereon.

[0079]FIG. 19 illustrates the sensing device 126, of the embodiment ofFIG. 10, connected to a control panel 188 which in turn has separateoutputs to an audible alarm device 190 and a display monitor 192 of acomputer. The computer may be used for infeeding information into thecontrol panel 188. When the sensing device 126 indicates a predeterminedincrease in weight of the biomedia strand 116 (FIG. 10), the audiblealarm 190 sounds. The monitor 192 shows a visual warning. If the sensingdevice 126 gives a progressive output signal indicative of the changingweight of the sensed strand 116, then the monitor 192 can give acontinuing indication of the state of the biomedia in the trickle tower.

[0080]FIG. 20 is an electrical schematic of the embodiment of FIGS. 12and 13, modified to include four valves associated with the middletrickle tower B, and including the biomass sensing arrangement of FIGS.14 to 18 incorporated in each trickle tower A, B, and C. The fourswitches 176 of trickle tower A are connected to a common junction 194,which is connected to a timer circuit 195 in a control panel 198. Thefour switches 176 of each of towers B and C are similarly connected totimer circuits 196, 197, respectively. The outputs from the timers 195to 197 feed into a programmable central processing unit CPU, outputsfrom which feed a circuit board 199 that in turn controls the operationof valve-actuating solenoids 201 to 212. Each of the valves 151 to 158in FIGS. 12 and 13 has its own individual solenoid, as shown in FIG. 20.Additionally, in FIGS. 12 and 13, valves B1 and B4 are connected betweenthe pipes 141 and 144 and the base tank 136 of trickle tower B, and theopen connections 159 and 160 are replaced by valves B2 and B3. Thevalves B1, B2, B3, B4 are operable by the solenoids 202, 205, 208, 211,respectively. When a switch 176 in one of the towers A, B, or C sends asignal to the CPU, the appropriate solenoids are actuated to cause thevalves 151 to 158 and B1 to B4 to change the sequence of flow throughthe towers. The sequence will follow the repeating patternA-B-C→B-C-A→C-A-B. On the other hand, to obtain the previously describedrepeating pattern with B always in the middle, i.e. A-B-C→C-B-A, the CPUis programmed to keep the valves B1, B4 closed and the valves B2, B3open throughout the sequence. The timers 195 to 197 are set so that oncea signal has passed through a particular timer to the CPU, there is apredetermined delay before another signal can pass through that timer.This delay may be two weeks or more, e.g. three months, depending on therate of atrophy of the biomass in the tower that just triggered thesequence change. The purpose of this delay is to stop hunting orpremature changes in the sequence, the delay giving the tower triggeringthe last weight signal sufficient time to reduce in biomass weight wellbelow the triggering threshold. The frequency at which the sequence istriggered to change depends upon the rate of growth of biomass on thebiomedia, which in turn depends, inter alia, on the content of thewastewater, the rate of flow of the supply of wastewater, the size ofthe trickle tower system including the number of towers, and theconstruction of the biomedia.

[0081] In a simplified but not as effective method, the weight sensingsystem can be omitted, and the sequence changing based on a timingprogram operated by the CPU at fixed, preset intervals.

[0082] It will be appreciated from the above, that the present inventionprovides better control over biomass build up by employing variousgrooming techniques, and some preferred embodiments of the inventionadvantageously provide automatic grooming. The automatic grooming of thepresent invention not only enables extended continuous processing to beachieved, but enables this to be done with improved efficiency ofprocessing, resulting overall in purer effluent.

[0083] The above-described embodiments, of course, are not to beconstrued as limiting the breadth of the present invention.Modifications, and other alternative constructions, will be apparentwhich are within the spirit and scope of the invention as defined in theappended claims.

What is claimed is:
 1. A wastewater treatment apparatus, comprising: aplurality of trickle towers containing biomedia; a plurality ofwastewater discharge means for discharging wastewater at upper ends ofthe trickle towers to enable the wastewater to pass down said biomedia;receptacles adjacent lower ends of the trickle towers for catchingwastewater falling from the biomedia; moving means for moving wastewaterfrom said receptacles to said discharge means to enable wastewater torecirculate through the trickle towers; and manifold means,interconnecting said trickle towers, for enabling wastewater to besequentially moved through said trickle towers in different selectivesequences.
 2. The apparatus of claim 1, wherein said biomedia comprisesvertically extending looped cord biomedia, and further comprisingtensioning means for holding said looped cord biomedia under tension. 3.The apparatus of claim 1, wherein said manifold means comprises a pipesystem.
 4. The apparatus of claim 1, wherein said manifold meansincludes valves, and further comprising a control system connected tosaid valves and programmable to selectively operate said valves.
 5. Theapparatus of claim 1, wherein said manifold means is connected to saidtrickle towers by selectively operable valves.
 6. The apparatus of claim1, further comprising sensing means for responding to accumulation ofbiogrowth on the biomedia in at least one of the trickle towers duringoperation.
 7. The apparatus of claim 6, wherein said sensing meanscomprises a weight sensitive element.
 8. The apparatus of claim 6,further comprising: signal means for creating a signal responsive tosaid sensing means; and an indicator responsive to said signal toprovide an indication of the accumulation of the biogrowth in said atleast one trickle tower.
 9. The apparatus of claim 6, wherein saidmanifold means includes at least one valve, and said sensing meanscauses actuation of said valve when said accumulation of biogrowthreaches a predetermined level.
 10. The apparatus of claim 1, wherein:said manifold means comprises pipes connected to said receptacles byvalves; and further comprising: sensing means for sensing increase inbiogrowth on said biomedia, and for causing at least some of said valvesto be actuated to change the sequence of flow of the wastewater throughsaid trickle towers upon said sensed increase in biogrowth reaching apredetermined level.
 11. The apparatus of claim 10, wherein said sensingmeans comprises a yieldable member yieldable to increase in weight of atleast a part of said biomedia.
 12. The apparatus of claim 1, furthercomprising weight sensitive means, responsive to increase in weight ofat least a part of said biomedia due to accumulation of biogrowththereon, for causing the sequence of movement of said wastewater throughsaid trickle towers to change.
 13. The apparatus of claim 1, furthercomprising means for independently sensing increase in biogrowth on thebiomedia in each tower, and for causing the sequence in which thewastewater moves through the trickle towers to be changed so that thetower with the largest biogrowth is placed last in the sequence.
 14. Awastewater treatment apparatus, comprising: a plurality of trickletowers, each tower containing one or more cells, and each cellcontaining a plurality of vertically extending strands of biomedia; saidtowers being interconnectable to enable the wastewater to pass throughthem in sequence; valves associated with said towers for changing saidsequence; and means, responsive to changes in weight of and connected toat least a part of the biomedia in at least one of said cells, forsensing increase in weight of said at least a part due to biogrowthforming thereon, and for causing operation of at least one of saidvalves to change said sequence when a predetermined weight increase issensed.
 15. The apparatus of claim 14, wherein said means includes aspring connected between said at least a part of the biomedia and thetower of that part, said spring at least partially supporting said part.16. A wastewater treatment apparatus, comprising: a trickle tower havinga support structure; strands of biomedia suspended from said structure,wastewater when being treated passing down said strands of biomedia; andmeans for sensing increase in growth of biomass on at least a portion ofsaid biomedia.
 17. The apparatus of claim 16, wherein said sensing meanssenses increase in weight.
 18. A method of treating wastewater,comprising the steps of: introducing a supply of wastewater into a firsttrickle tower containing biomedia and circulating this wastewatertherethrough, the wastewater passing down through the biomedia andbecoming partially treated; after a time, passing the wastewater to asecond trickle tower containing biomedia and circulating the wastewatertherethrough to further treat the wastewater; allowing biogrowth tobuild on the biomedia in said trickle towers; sensing change in weightof at least a part of the biomedia in said first trickle tower due tothe increase in biogrowth; and upon said change reaching a predeterminedvalue, switching the sequence of flow of the wastewater through thetrickle towers by introducing the supply of wastewater into the secondtrickle tower for the first partial treatment thereof.
 19. The method ofclaim 18, wherein there are more than two trickle towers in the sequenceof flow of the wastewater through the trickle towers, and the sequenceof flow is switched each time a sensed increase in weight in one of thetrickle towers reaches a predetermined value.
 20. A method of treatingwastewater, comprising the steps of: passing wastewater sequentiallythrough a plurality of trickle towers, the wastewater to be treatedbeing introduced at one tower and the fully treated wastewater exitingat another tower; monitoring the growth of biogrowth in the towers; andwhen the monitored growth of biogrowth in any particular tower reaches apredetermined value, switching the sequence in which the wastewaterpasses through the plurality of trickle towers to cause the fullytreated wastewater to exit the plurality of trickle towers at thisparticular tower.